Hickory

Shagbark hickory, Carya ovata Bitternut hickory, Carya cordiformis

The volume in hickory has increased steadily over the last several decades and is aging.

Since 1983, the volume in large trees has more than tripled while the volume in small trees has only increased 21%. Growth rates haven’t changed significantly since 1983 but mortality has quadrupled. Hickory accounts for about 1.4% of volume and growth but only 0.7% of mortality and 0.9% of removals. The volume of bitternut hickory is expected to decrease in the next 40 years while the volume of shagbark hickory should increase substantially. Hickory is not a prominent timber species, accounting for only 0.3% of roundwood production in 2009. Although removals have increased five-fold since 1983, we harvest much less hickory compared to other species. Hickory wood has the highest density of all species in Wisconsin and therefore may be a valuable source of woody biomass.

• How has the hickory resource changed? Growing stock volume and diameter class distribution • Where is hickory found in Wisconsin? Growing stock volume by region with map • What kind of sites does hickory grow on? Habitat type and site index distribution

• How fast is hickory growing? Average annual net growth: trends and ratio of growth to volume

• How healthy is hickory in Wisconsin? Average annual mortality: trends and ratio of mortality to volume • Does hickory have any disease or pest issues? 100 Canker Disease: biology, symptoms and impact • How much hickory do we harvest? Roundwood production by product and ratio of growth to removals • How much hickory biomass do we have? Aboveground biomass by region of the state Division of Forestry • Can we predict the future of beech? WI Dept of Natural Resources December 2019 Modelling future volumes

“How has the hickory resource changed?” Growing stock volume and diameter class distribution by year

The growing stock volume of hickory in 2018 was about 301 million cubic feet or 1.4% of total statewide volume (chart on right). The Growing stock volume of hickory volume of hickory has increased steadily over the past few decades, 350 55% since 1983 and 37% since 1996. 300 250 The hickory resource is maturing; the total volume in small growing 3 stock (5-12.9 inches dbh) has increased by 19% since 1983 while the 200 volume in large trees (13+ inches dbh) has more than tripled (chart 150 Million ft below left). 100 50 The number of sawtimber hickory has increased by 49% since 2004 0 while the number of saplings has decreased by 7% (chart below 1983 1996 2004 2011 2018

right). Lack of regeneration may affect long term sustainability of Growing stock volume (million cubic feet) by inventory year. both species. Source: USDA Forest Inventory and Analysis data

Volume of hickory by diameter class Percentage change in tree numbers Seedling Sapling Pole Sawtimber 120 100% 100 5-8.9 50% 3 80 9-12.9 13-16.9 60 0% 17-20.9 Million ft 40 21-24.9 -50% 20 25+ 0 -100% 1983 1996 2011 2018 Bitternut hickory Shagbark hickory Total hickory

Growing stock volume (million cubic feet) by diameter class (inches). Percentage change in the number of live trees by size class between 2004 and 2018. Source: USDA Forest Inventory and Analysis data. Source: USDA Forest Inventory and Analysis data 2004 and 2018.

“Where is hickory found in Wisconsin?” Growing stock volume by region with map

About 59% of hickory volume is shagbark hickory (Table 1). Most hickory occurs in southwest Wisconsin with only 4% in the northern part of the state.

Shagbark hickory is found almost exclusively on the oak / hickory forest type whereas bitternut hickory is also an important component of the maple / beech / birch type.

Table 1. Growing stock volume (million ft3) by species and region of the state.

North North South South Percent Species Central Total east west east west of total Bitternut hickory 29 6 7 15 66 122 41%

Shagbark hickory 16 - - 51 112 178 59%

Total 45 6 7 66 178 301 100%

Percent of total 15% 2% 2% 22% 59% 100%

Source: USDA Forest Service, Forest Inventory and Analysis 2018

For a table on Volume by County go to: http://dnr.wi.gov/topic/ForestBusinesses/documents/tables/VolumeCountySpecies.pdf “What kind of sites does hickory grow on?” Habitat type and site index distribution

About two-thirds of both bitternut and shagbark hickory growing stock volume is found on dry- mesic to mesic and mesic habitat types (chart below). Shagbark hickory is a little more likely to be found on drier sites, whereas bitternut hickory is more often found on wetter sites.

Bitternut hickory 0% Shagbark hickory 0% 0% 0% 0% 0% Very Dry to Dry 11% 15% Dry 30% 31% 18% Dry to Dry-mesic Dry-mesic 24% Dry-mesic to Mesic Mesic 2% 34% 3% 27% Mesic to Wet-mesic 5% 0% Wet-Mesic to wet Undefined

Percent distribution of growing stock volume by habitat type group1 (USDA Forest Inventory & Analysis data).

Hickory percent of volume by site index 40% 35% Bitternut hickory growing stock volume is found on slightly richer 30% sites (chart on left). Over 86% of bitternut hickory volume is 25% located on sites with a site index greater than 60. Only 62% of 20% All Species shagbark hickory volume is on sites with a site index greater than 15% Bitternut hickory 60. 10% Shagbark hickory 5% 0% The average site index by volume for bitternut hickory is 74 much <41 41 - 50 51 - 60 61 - 70 71 - 80 81 - 90 90+ higher than the average for all species, 66. The average for Site Index Class shagbark hickory is 65.

Percent distribution of growing stock volume by site index class (USDA Forest Inventory & Analysis data).

1For more information on habitat types see Schmidt, Thomas L. 1997. Wisconsin forest statistics, 1996. Resource Bulletin NC-183. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central

“How fast is hickory growing?”

Average annual net growth: trends and ratio of growth to volume

Average annual net growth of hickory The average annual net growth of hickory is about 8.0 million cubic feet per year, representing 1.4% of statewide volume growth (chart on right). Volume growth has increased 10 slightly since 1983. 9 8 7 Almost all volume growth for hickory occurs in southern 3 6 Wisconsin (Table 2), but the highest growth to volume ratio 5 is currently in northwest Wisconsin. 4 Million ft 3 2 1 0 Table 2. Average annual net growth (million ft3/year) of growing stock and the 1983 1996 2011 2018 ratio of growth to volume by region of the state. Average annual net growth (million cubic feet). Percent of Ratio of growth Source: USDA Forest Inventory & Analysis data Region Net growth Total to volume

Northeast -0.1 - - Northwest 0.3 3% 4.1% The ratio of growth to volume for hickory is 2.7%, almost

Central 1.3 16% 2.8% equal to the statewide average of 2.6% for all species.

Southwest 4.8 60% 2.7%

Southeast 1.8 22% 2.7%

Statewide 8.0 100% 2.7%

Source: USDA Forest Inventory and Analysis 2018 For a table of Average annual growth, mortality and removals by region go to: http://dnr.wi.gov/topic/ForestBusinesses/documents/tables/GrowthMortalityRemovals.pdf

“How healthy is hickory in Wisconsin?” Average annual mortality: trends and ratio of mortality to volume

Average annual mortality of hickory The average annual mortality of hickory, about 2.1 million cubic 6 feet per year from 2012 to 2018, has increased four-fold since 5 1983 (chart on right). The percent of statewide mortality, 0.9%, 4

is much less than the percent of total volume in the state, 1.4%. 3

3 The ratio of mortality to volume is 0.7% for hickory species (Table Million ft 3). This rate is much lower than the statewide average of 1.1% 2 for all species. However, the difference between the mortality 1 to volume ratio for bitternut hickory (1.4%) and shagbark hickory (0.2%) is very large. 0 1983 1996 2011 2018

Average annual mortality (million cubic feet) by inventory year. Error bars represent the 67% confidence interval. Source: USDA Forest Inventory & Analysis data

Table 3. Mortality, volume and the ratio of mortality to volume. Average annual Volume of growing Mortality Species mortality (ft3) stock (ft3) / volume Bitternut hickory 1,709,648 122,083,638 1.4%

Shagbark hickory 356,622 178,513,902 0.2%

Total hickory 2,066,270 300,597,540 0.7%

Source: USDA Forest Inventory & Analysis data

For a table of Average annual growth, mortality and removals by region go to: http://dnr.wi.gov/topic/ForestBusinesses/documents/tables/GrowthMortalityRemovals.pdf

“Does hickory have any major disease or pest issues?” Thousand Canker Disease: biology, symptoms and impact

Since 2005, dieback and mortality of bitternut and shagbark hickory have been reported in Wisconsin. Although affecting both species, mortality appears to be more prevalent for bitternut hickory (Figure on right). Mortality and

dieback peaked in Wisconsin in 2011, possibly related to drought in 2003-2009. Since 2011, mortality has decreased for both species.

Symptoms progress rapidly from thinning crowns to branch mortality to complete tree mortality. Epicormic branches often sprout only to die later, and sunken

cankers can often be found on these trees. Tree mortality occurs two or three Left: Annual mortality rates by species and inventory year. Right. Percentage of hickory years after an initial appearance of symptoms. trees with crown dieback over 5% by inventory year. Source: USDA Forest Inventory and Analysis

Recent research indicates that hickory mortality is due to a complex of biotic and abiotic factors, including the hickory bark beetle, Scolytus quadrispinosus, and other insects, and the fungus Ceratocysis smalleyi (Figure on left). Scolytus quadrispinosus, native to Wisconsin, is known as the most destructive insect to hickory in the eastern United States.

Larvae of this insect attack and kill hickory trees by mining the phloem. The adult bark beetle provides the entry and infection court for the fungus on susceptible hickories. This interaction results in numerous bark cankers and debilitating xylem lesions that may lead to rapid crown decline and tree death. Severe drought, as we saw in Wisconsin from 2003 to 2009, is thought to contribute to this disease by leading to beetle population buildup.

The number of cankers on a tree can be significant and cankers can be found through- Upper left: Hickory bark beetle. Upper Right: Fungal penetration out the tree, giving it an unofficial name of ‘Thousand Canker Disease.’ deep into the wood. Lower left: Branch dieback and mortality. Lower right. Larval galleries & fungal staining (Photos: E. Smalley) “How much hickory do we harvest?” Roundwood production by product: trends and ratio of growth to removals

In 2013, Wisconsin produced 891,000 cubic feet of hickory roundwood or about 0.3% of the state’s total volume (chart on right ). Almost 90 of this was in sawlogs and veneer with lesser amounts of pulpwood and fuelwood.

Between 2004 and 2013, sawlog/veneer production decreased by 14% and pulpwood production decreased by 55%

Volume of roundwood. * Miscellaneous products include poles, posts and pilings. Source: Ronald Piva, USDA Forest Service, Northern Research Station, St. Paul MN

Ratio of growth to removals: Hickory 14.0 12.0 12.4 Removals of hickory were 2.7 million cubic feet per year from 2012 to 2018. 10.0 Slightly over 50% of this was shagbark hickory. 8.0 6.0 The ratio of average annual net growth to removals decreased from 34.9 in 4.0 1983 to 2.9 in 2018 (chart on left), mostly due to a more than quadrupling 3.7 of harvest levels. The ratio of growth to removals for hickory is twice as 2.0 3.4 2.9 high as the average of 1.9 for all species in the state. 0.0 1983 1996 2011 2018

Source: USDA Forest Inventory & Analysis data For a table of Average annual growth, mortality and removals by region go to: http://dnr.wi.gov/topic/ForestBusinesses/documents/tables/GrowthMortalityRemovals.pdf

“How much hickory biomass do we have?” Aboveground biomass by region of the state

here were 12.1 million short tons of aboveground biomass in live trees in the T hickory group in 2018, an increase of 45% from 1983. This is equivalent to approximately 6.0 million tons of carbon and represents 1.9% of all

aboveground carbon statewide. As with volume, most hickory is located in southern Wisconsin (chart below).

Biomass of all live trees: Hickory The density of hickory wood is the highest of all species with a ratio of biomass to volume of 45 oven-dry lbs. per cubic foot (ODP/ft3). The 8 average for all hardwoods is about 37 ODP/cubic 7 feet and for all species is 33 ODP/cubic feet.

6 pproximately, 68% of all hickory biomass is 5 A located in the main stem, 8% in saplings, 5% in 4 stumps, and 19% in the top branches. 3

2 he high density of hickory wood may make it a Millionoven dry tons T 1 valuable species for biofuel production. 0 Central Northeast Northwest Southeast Southwest 1983 1996 2011 2018

Biomass (above ground dry weight of live trees >1 in dbh, short tons) by year and region of the state. Source: USDA Forest Inventory & Analysis data. For a table of Biomass by County go to: http://dnr.wi.gov/topic/ForestBusinesses/documents/tables/BiomassByCounty.pdf

“Can we predict the future of hickory?”

Predicted volumes based on current rates of mortality and harvest

he 5-year ratios of mortality to volume, removals to volume and growth to volume T bitternut hickory shagbark hickory All species are significantly lower for basswood compared to all species in the state (chart on 20% right). 18% 16% The Forest Vegetation Simulator (FVS1) was used to predict future volumes of 14% 12% bitternut and shagbark hickory through 2054 (chart below). Bitternut hickory 10% volume decreases by 18% in the next 40 years whereas shagbark hickory volume 8% increases by 69%. The decrease in bitternut hickory may very well be due to high 6% 4% sawtimber removals. For instance, the 5-year ratio of sawtimber removals to 2% volume is almost eight times higher for bitternut hickory (11.5%) compared to 0% Growth/volume Mortality/volume Removals/volume shagbark hickory (1.5%) and is one of the highest ratios of all species.

Predicted growing stock volume of hickory 350 295 300

250

200 174

150 116 94 100

Million cubic feet cubic Million 50

0 2014 2019 2024 2029 2034 2039 2044 2049 2054

Shagbark hickory Bitternut hickory

The Forest Vegetation Simulator is a forest growth and yield simulation model created by the USDA Forest Service, see http://www.fs.fed.us/fmsc/fvs/.